This invention pertains to drive systems for delivering media during a printing process. More particularly, this invention relates to precise transport and registration of print media during a printing process such as when printing one or more image planes onto a sheet of paper with a color laser printing system.
Color image printing systems are known in the art. One color image printing system comprises a color laser, or electrophotographic, printer. Color laser printers generate sufficient text and graphics quality for most business applications. However, color laser printers typically require complex and expensive mechanisms when forming and aligning overlaid color frames. Hence, color laser printers are not sufficiently economical for many applications.
One problem encountered with color laser printers relates to registration of individual color image planes that generate a printed color page. Typically, three or four distinct color image planes are somehow imaged and transferred onto a common piece of paper in order to generate a color image. In some cases, a yellow, a magenta and a cyan color image plane are each imaged and transferred onto a common piece of paper. In other cases, a black, a yellow, a magenta and a cyan color image plane are each imaged and transferred. Irrespective of whether individual color image planes are serially or concurrently transferred onto a piece of paper, registration of individual color image planes is very important, and even slight variations between image planes can cause hue and density shifts throughout a printed page.
One type of color image printing system builds up four different colored image planes onto a well-controlled substrate before transferring the generated image onto a piece of paper. One exemplary printing system comprises a Hewlett-Packard Color LaserJet 5, manufactured by Hewlett-Packard Co. of Palo Alto, Calif. Such exemplary printing system builds up a color image onto a page size photoconductor drum. The generated image comprises four distinct colors: yellow, magenta, cyan and black. Four developers are used to produce the four colors, with four distinct photoconductor drum rotations being needed to accumulate the four-color toner images. Such printing system delivers four colors onto a photoconductor drum which are transferred in one step onto a sheet of paper. This results in a relatively low cost technique for achieving a four pass color laser printer having excellent plane-to-plane registration.
Another type of color image printing system builds up an image on a page size intermediate transfer medium. One example a Tektronix Phaser 560, manufactured by Tektronix of Wilsonville, Oreg. However, this system uses an intermediate transfer medium which increases cost and complexity. Yet another type of color image printing system comprises a Xerox C55 color laser printer. Such laser printer fixes a sheet of paper onto a drum in order to achieve plane-to-plane registration of successively colored image planes. However, this system adds considerable size and complexity to a color laser printer.
Recent attempts have been made to improve precise positioning of print media to enhance registration of image planes that are deposited atop the print media. U.S. Pat. No. 5,978,642 discloses a shuttle type paper drive for multiple pass color laser printing which uses a grit shaft and pinch rollers to accurately move the print media along a bidirectional travel path and register the print media and multiple image planes. However, such shuttle type paper drive requires a significant top or bottom margin because the grit shaft must maintain contact with the print media at a pinch zone. Accordingly, there exists a significant bottom margin area which cannot be used for color printing.
Each of the above-mentioned printing systems increases the size of the printer or increases the complexity or cost of the printer. Furthermore, the shuttle type paper drive in U.S. Pat. No. 5,978,642 requires excessive margin areas on the print media. Therefore, there exists a need to provide a reduced cost and complexity technique for more accurately transporting and registering image planes onto a print media. For example, there exists a need for improved accuracy of image plane registration and a need to minimize margin size so as to reduce paper waste when moving a sheet of paper about a travel path of a multiple pass color laser printer.
A recirculating type, or shuttle type, paper drive provides a relatively low cost technique for precisely moving and registering image planes for a multiple pass color laser printer. According to one implementation, a four pass color laser printer achieves improved precision registration for most types of printable paper.
According to one aspect, a print media sheet feeder system includes an edge guide grit belt to guide and move a sheet of media along a travel path of a peripheral device, and at least one pinch roller provided for co-rotation with the grit belt, wherein the sheet of media is moved between the belt and the roller along one edge.
According to another aspect, a printing system for printing at least one image plane onto a sheet of print media includes an electrophotographic print engine comprising a photoconductor drum and a transfer roller configured to interact in co-rotation with the drum during transfer of an image plane from the drum onto a sheet of print media passed therebetween, and a print media sheet feeder system includes an edge guide grit belt to guide and move a lateral edge of a sheet of media along a travel path of a peripheral device and a pinch roller provided for co-rotation with the belt, wherein the edge guide grit belt and the pinch roller cooperate to move the sheet of media along the travel path.
According to yet another aspect, a laser printer media drive system includes a drive motor, a drive wheel, a follower wheel, a grit belt, and a pinch roller. The drive wheel is driven by the drive motor. The follower wheel is disposed from the drive wheel. The grit belt is tensioned about the drive wheel and the follower wheel. The pinch roller is biased into engagement with the grit belt for co-rotation with the grit belt as a sheet of media is received therebetween. The drive motor and the drive wheel cooperate to move the grit belt along a lateral edge of a sheet of media to move the media along a travel path during a print operation.
One advantage is provided by precisely transferring a sheet of print media between successive passes against one or more photoconductor drums using an edge guide grit belt while transferring successive color image planes onto the sheet of print media so as to ensure precise registration between successive color image planes when forming an image.
Other features and advantages of the invention will become apparent to those of ordinary skill in the art upon review of the following detailed description, claims, and drawings.